• Korean Journal of Heritage: History & Science
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• v.56 no.3
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• pp.214-232
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• 2023

Stromatolite at the Daegu Catholic University, Gyeongsan was designated as a natural monument in December 2009 because it was very excellent in terms of rarity, accessibility, preservation and scale. From the time of designation, the necessity of confirming the lateral extension of the stromatolite beds with the excavation of the surrounding area, and preparing a preservation plan was raised. Accordingly, the Cultural Heritage Administration conducted an investigation of the scale, production pattern, and weathering state of stromatolites with an excavation from April to December 2022, and based on this, suggested natural heritage values and conservation and use plans. The excavation was carried out in a 1,186m² area surrounding the exposed hemispherical stromatolite (approximately 30m2). Stromatolites are continuously distributed over the entire excavation area, and hemispherical stromatolites predominate in the eastern region, and the distribution and size of hemispherical domes tend to decrease toward the west. These characteristics are interpreted as a result of long-term growth in large-scale lakes, where stratiform or small columnar domes continued to grow and connect with each other, finally forming large domes. Consequently, large and small domes were distributed on the bedding plane in clusters like coral reefs. The growth of plants and lichens, as well as small-scale faults and joints developed on the stromatolite bedding surface, is the main cause of accelerated weathering. However, preservation treatment with chemicals as with dinosaur footprints or dinosaur egg fossil sites is not suitable due to the characteristics of stromatolites, and preservation with the installation of closed protection facilities should be considered. This excavation confirmed that the distribution, size and value of stromatolites are much larger and higher than at the time of designation as a natural monument. Therefore, additional excavation of areas by experts that could not be excavated due to the discovery of buried cultural properties (stone chamber tombs) and reexamination of the expansion designation of natural monuments are required.

• Journal of Korean Association for Spatial Structures
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• v.2 no.1 s.3
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• pp.85-92
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• 2002

Two way grid single-layer domes are of great advantage in fabrication and construction because of the simple fact that they have only four members at each junction. But, from a point of view of mechanics, the rectangular latticed pattern gives rise to a nonuniform rigidity-distribution in the circumferential direction. If the equivalent rigidity is considered in the axial direction of members, the in-plane equivalent shearing rigidity depends only on the in-plane bending rigidity of members and its value is very small in comparison to that of the in-plane equivalent stretching rigidity. It has a tendency to decrease buckling -strength of dome considerably by external force. But it is possible to increase buckling strength by the use of roofing covering materials connected to framework. In a case like this, shearing rigidity of roofing material increases buckling strength of the overall structure and can be designed economically from the viewpoint of practice. Therefore, the purpose of this paper, in Lamella dome and rectangular latticed dome that are a set of 2-way grid dome, is to clarify the effects of roofing covering materials for increasing of buckling strength of overall dome. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems. The conclusion were given as follows: 1. In case of Lamella domes which have nearly equal rigidity in the direction of circumference, the rigidity of roofing covering materials does not have a great influence on buckling-strength, but in rectangular latticed domes that has a clear periodicity of rigidity, the value of its buckling strength has a tendency to increase considerably with increasing rigidity of roofing covering materials 2. In case of rectangular latticed domes, as rise-span-ratio increases, models which is subjected to pressure -type-uniform loading than vertical-type-uniform loading are higher in the aspects of the increasing rate of buckling- strength according to the rate of shear reinforcement rigidity, but in case of Lamella dome, the condition of loading and rise-span-ratio do not have a great influence on the increasing rate of buckling strength according to the rate of shear reinforcement rigidity.

• The Journal of the Petrological Society of Korea
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• v.21 no.3
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• pp.367-383
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• 2012

The Gyeongsang Arc is the most notable of the Korea Arc that is composed of several volcanic arcs trending to NE-SW direction in the Korean peninsula. The Hayang Group has many volcanogenic interbeds of lava flows by alkaline or calc-alkaline basaltic volcanisms during early Cretaceous. Late Cretaceous calc-alkaline andesitic and rhyolitic volcanisms reconstructed the Gyeongsang Arc that consist of thick volcanic strata on the Hayang Group in The Gyeongsang Basin. The volcanisms characterize first eruptions of basaltic and andesitic lavas with small pyroclastics, and continue later eruptions of dacitic and rhyolitic ash-fall and voluminous ash-flow with some calderas and then domes and dykes. During the Early Cretaceous (about 120 Ma), oblique subduction of the Izanagi plate to NNW from N direction results in sinistral strike-slip faults to open a pull-apart basin in back-arc area of the Gyeongsang Arc, in which erupted lava flows from generation of magma by a decrease in lithostatic pressure. Therefore the Gyeongsang Basin is interpreted into back-arc basin reconstructed by a continental rifting. Arc volcanism began in about 100 Ma with exaggeration of the back-arc basin in the Gyeongsang, and then changed violently to construct volcanic arcs. During the Late Cretaceous (about 90 Ma), orthogonal subduction of the Izanagi plate to NW from NNW direction ceased development of the basin to prolong violent volcanisms.

• The Journal of the Petrological Society of Korea
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• v.21 no.4
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• pp.385-396
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• 2012

Jeju island is the biggest volcanic island in Korea and there are over 455 Quaternary monogenetic volcanoes, of which approximately 373 volcanoes(82.0%) are cinder cones. Other volcanic forms in the island include sharp-pointed lava cone without crater(9 volcanoes; 2.0%), shield volcanoes(27 volcanoes; 5.9%), tuff rings(17 volcanoes; 3.7%), tuff cones(3 volcanoes; 0.7%), a maar(1 volcano; 0.2%) and lava domes(25 volcanoes; 5.5%). The monogenetic volcanoes include 15 small nested cinder cones(aloreum). The monogenetic volcanoes are more abundant in the eastern part of the island than in the western part. If the main cause of the weathering such as precipitation affected the shape of the monogenetic volcanoes, more monogenetic volcanoes(BC, CC, DC, etc.) are supposed to be present in the southern part that have more precipitation than in the northern part. But the distribution of the monogenetic volcanoes shows no difference between the southern and the northern parts. So we suggest that the difference of the climatic conditions did not affect the distribution or the shape of cinder cones. Tuff rings, tuff cones and a maar are distributed beneath the island or in the low-altitude areas along the shore although cinder cones are distributed in the interior of the island. This means that the volcanic activity which formed the monogenetic volcanoes resulted from either phreatomagmatic eruption or magmatic (hawaiian or strombolian) eruptions depending on the reaction with water (underground water or shallow waters). The distribution of the monogenetic volcanoes according to the altitude shows that 253(55.6%) volcanoes occur in low-lying coastal areas at an altitude below 300 m, 110(24.2%) in a middle mountainous area at an altitude between 300~600 m and 92(20.2%) in a high mountainous area at an altitude above 600 m. So more than half of monogenetic volcanoes are distributed in low-lying coastal areas.